We are conducting genetics studies of the expression of alkaline phosphatase in E. coli. These include studies of mutants which may affect the regulation, secretion, and processing of alkaline phosphatase. In our work, we are using gene fusions between the alkaline phosphatase structural gene and the lactose operon. The use of these gene fusions has proven invaluable to help us determine the step in alkaline phosphatase gene expression which is altered in a particular mutant. For instance, some mutants have been shown to be blocked in transcription of the alkaline phosphatase structural gene, and other mutants have been shown to be blocked in some post-transcription and post-translation step of alkaline phosphatase expression. In some cases, we are using mutants which have resulted from the insertion of a transposable drug resistance element into a particular gene of interest.